Heretofore, organo(poly)siloxanes having various organic groups introduced in a portion of their structures have been developed by use of properties specific to dimethylpolysiloxane typified by silicone oil.
Of them, organopolysiloxane having a hydrophilic organic group introduced therein (e.g., polyoxyethylene/polysiloxane copolymers) has both hydrophilic-hydrophobic moieties in addition to hydrophobicity derived from the siloxane site and exhibits excellent surface activities. Therefore, such organopolysiloxane is generally used as a silicone-based surfactant, particularly in the field of cosmetics.
Various compounds have been developed and studied so far, for example, as organo(poly)siloxane derivatives having a carboxyl group, which is a hydrophilic organic group. As typical examples, organosiloxane derivatives having a carboxyl group introduced in the side chain of a linear polysiloxane structure are widely known. In recent years, siloxane dendrimers having a carboxyl structure have been reported as one example of such compounds (see e.g., Patent Literatures 1 to 3). Furthermore, it has also been reported that a compound obtained by neutralizing carboxyl-modified silicone with triethanolamine has an emulsification capacity (see e.g., Non-Patent Literatures 1 and 2).
On the other hand, in the field of cosmetics, it has heretofore been known that a gel structure is formed in a surfactant/higher alcohol/water system (see e.g., Non-Patent Literature 3). Cosmetics provided with excellent texture in use by the collapse of the gel structure, etc., are being developed. However, all the conventional gel compositions were less than satisfactory in terms of texture in use, due to problems such as formation of a relatively rigid gel structure. Thus, use of the silicone-based surfactants is expected to produce the effect of further improving texture in use such as skin penetration and stickiness. However, none of the conventional silicone-based surfactants are known to form a gel structure in the surfactant/higher alcohol/water system.
Patent Literature 1: Japanese Unexamined Patent Publication 2000-072784
Patent Literature 2: Japanese Unexamined Patent Publication 2000-239390
Patent Literature 3: Japanese Unexamined Patent Publication 2001-213885
Non-patent Literature 1: Kazuki KAGESHIMA and Toshiyuki SHIMIZU, “Application of carboxyl-modified silicone as surfactant in emulsification,” Fragrance Journal extra edition 19 (2005): 125-130
Non-patent Literature 2: Kazuki KAGESHIMA, Harumi SAKAMOTO, and Toshiyuki SHIMIZU, “Application of carboxyl-modified silicone as surfactant in cosmetic field,” Journal of SCCJ Vol. 34 No. 4 (2003): 309-314
Non-patent Literature 3: Seiji FUKUSHIMA, Physical chemistry of cetyl alcohol (FRAGRANCE JOURNAL LTD.) Ch. 6, 76-88.